The present invention broadly relates to the art of injection molding of injection molded parts containing insert elements molded therein, especially injection molded parts formed of a thermosetting plastic or duroplast, and specifically pertains to a new and improved method of, and apparatus for, injection molding of such injection molded parts.
Examples of such injection molded parts are mass produced parts formed of electrically insulating thermosetting plastics containing imbedded or cast therein metallic threaded bushings or sleeves, such as for instance components of sockets, plugs and the like, or, however, parts of plastic housings in which, for instance, there are cast metallic threaded bushings, centering pins and sleeves.
In the art of injection molding of plastics there has already been employed the so-called "cassette or cartridge principle". This principle strives to simplify the introduction of the insert elements, about which there is cast the plastic material, into the hollow mold compartments. This technique contemplates utilizing a reusable templete or stencil, namely the "cassette" or cartridge" which retains the insert elements in a desired number and relative position, and introducing such "cassette", with the injection mold open, in front of the hollow mold compartments. Thereafter, by causing the closure unit to carry out a predestined work stroke the insert elements are ejected out of the cassette and displaced into the hollow mold compartments, whereupon the injection mold provided with the insert elements is ready for a new injection mold cycle. With the heretofore known equipment, working with this principle, the introduction of the insert elements requires a considerable amount of time which is not negligible, considerably reducing the production capacity of the injection molding machine in comparison to injection molding machines which injection mold parts without insert elements. In reality the mode of operation of the heretofore known apparatuses -- starting from the open and empty injection mold -- can be considered as encompassing the following procedures:
1. Bringing a cassette equipped with insert elements in front of the one mold half of the injection mold. PA1 2. Closing the injection mold and thereafter simultaneously injecting the insert elements out of the cassette and transferring such insert elements into the hollow mold compartments. PA1 3. Opening the injection mold and removing the now emptied cassette. PA1 4. Closing the injection mold, thereafter injecting the plastic into the hollow mold compartments and then setting or hardening the injection molded parts. PA1 5. Opening the injection mold and ejecting the injection molded parts out of the injection mold so that the latter is again empty.
Hence, it will be recognized when injection molding injection molded parts which do not contain therein cast insert elements, it is only necessary to perform the aforementioned steps 4 and 5, whereas, on the other hand, with the known apparatuses the steps 1 to 3 constitute a significant unproductive expenditure in time.